CSEDI: Constraining the mechanisms of melt transport, storage, and crustal contamination from temporal geochemical variations in monogenetic vents

单成因喷口是相对较小的火山，在几个月到几年的时间里，一次喷发就会活跃起来，与之相反，更典型的火山是在多次不同的喷发中逐渐形成的，通常间歇性地活跃数万年或更长时间。单成因喷口常成簇状出现，是许多构造环境中常见的火山活动类型。几个单基因喷口田出现在人口密度高的地区或附近，包括新西兰的奥克兰和墨西哥的墨西哥城。因此，单成因喷口代表了一个重大的火山危险。先前的研究表明，在一次喷发过程中，从单一成因喷口喷出的火山灰和熔岩的成分经常随着时间的推移而系统地变化。这种变化的原因尚不清楚，但它很可能反映了熔体产生和从地幔中提取的过程，或熔体在大陆地壳中的储存和喷发前的熔体/地壳相互作用。更好地了解在单基因喷口喷发中观察到的化学变化的原因，将使科学家更好地了解这些火山的管道系统。这反过来又可以更好地预测可能预示即将爆发的前兆信号。本研究将熔体运输和储存过程的数值模拟与对特定单成因喷口喷发序列喷发物质的详细地球化学分析相结合，以更好地约束单成因喷口喷发前的熔体生成、上升和储存过程。在单成因喷发序列中产生化学变化的不同假设机制（例如，地幔中的反应性熔体运输或喷发前位于地壳浅层的岩浆层的递进式排水）将产生不同的时间化学变化。我们将把模型预测与观测结果进行比较，以约束这些变化的可能起源，然后利用观测到的变化提取与熔体产生、运输和储存相关的重要变量的信息，如地幔源区化学非均质性的大小、地壳中岩浆储存室的体积和几何形状，以及熔体注入地壳和随后储存的岩浆喷发之间的时间间隔。这些信息可以用于未来的研究，以预测可能预示即将爆发的最可能的信号（例如，岩浆注入引起的地面向上变形），以及这些信号与实际爆发之间可能的时间滞后。因此，拟议的研究既提高了我们对地质上重要和广泛的大陆火山作用类型的总体理解，也提高了我们评估和规划未来可能发生的单基因喷口喷发固有风险的能力。

Monogenetic vents are relatively small volcanoes that are active for a single eruption over a period of a few months to a few years, in contrast to more typical volcanoes that are gradually built up over many different eruptions and which are typically intermittently active for 10s of thousands of years or longer. Monogenetic vents often occur in clusters, and are a common type of volcanism in many tectonic settings. Several monogenetic vent fields occur in or near high-population-density areas, including Auckland, New Zealand and Mexico City, Mexico. Therefore, monogenetic vents represent a significant volcanic hazard. Previous studies have shown that the compositions of the ash and lava erupted from a monogenetic vent during the course of an eruption often varies systematically over time. The cause of this variability is not clear, but it most likely reflects either processes involved in melt generation and extraction from the mantle, or melt storage in the continental crust and melt/crust interaction prior to eruption. A better understanding of the cause(s) of the chemical variations observed in monogenetic vent eruptions would provide scientists with a better understanding of the plumbing system that feeds these volcanoes. This in turn will allow better prediction of the precursor signals that may signal an impending eruption.This study will combine numerical modeling of melt transport and storage processes with detailed geochemical analyses of material erupted from selected monogenetic vent eruptive sequences to better constrain the processes of melt generation, ascent, and storage that precede the eruption of monogenetic vents. Different hypothesized mechanisms for generating chemical variations in monogenetic vent sequences (e.g., reactive melt transport in the mantle or progressive draining of magma sills that are emplaced in the shallow crust prior to eruption) will produce different temporal chemical variations. We will compare model predictions with observations to constrain the likely origin of these variations, and then use the observed variations to extract information on important variables related to melt generation, transport, and storage such as the size of chemical heterogeneities in the mantle source region, the volume and geometry of magma storage chambers in the crust, and the time interval between melt injection into the crust and subsequent eruption of this stored magma. This information can be used in future studies to predict the most likely signals that may indicate an impending eruption (e.g., upward ground deformation due to magma injection) as well as the likely time lag between these signals and an actual eruption. The proposed study with therefore both improve our overall understanding of a geologically important and widespread style of continental volcanism, and improve our ability to evaluate and plan for the risks inherent in possible future monogenetic vent eruptions.